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Revision 1.38 by root, Wed Jun 6 18:16:52 2007 UTC vs.
Revision 1.59 by root, Mon Aug 27 01:49:01 2007 UTC

9 # exported functions, they croak on error 9 # exported functions, they croak on error
10 # and expect/generate UTF-8 10 # and expect/generate UTF-8
11 11
12 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref; 12 $utf8_encoded_json_text = to_json $perl_hash_or_arrayref;
13 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text; 13 $perl_hash_or_arrayref = from_json $utf8_encoded_json_text;
14
15 # objToJson and jsonToObj aliases to to_json and from_json
16 # are exported for compatibility to the JSON module,
17 # but should not be used in new code.
18 14
19 # OO-interface 15 # OO-interface
20 16
21 $coder = JSON::XS->new->ascii->pretty->allow_nonref; 17 $coder = JSON::XS->new->ascii->pretty->allow_nonref;
22 $pretty_printed_unencoded = $coder->encode ($perl_scalar); 18 $pretty_printed_unencoded = $coder->encode ($perl_scalar);
85 81
86package JSON::XS; 82package JSON::XS;
87 83
88use strict; 84use strict;
89 85
90BEGIN {
91 our $VERSION = '1.23'; 86our $VERSION = '1.5';
92 our @ISA = qw(Exporter); 87our @ISA = qw(Exporter);
93 88
94 our @EXPORT = qw(to_json from_json objToJson jsonToObj); 89our @EXPORT = qw(to_json from_json);
95 require Exporter;
96 90
97 require XSLoader; 91use Exporter;
98 XSLoader::load JSON::XS::, $VERSION; 92use XSLoader;
99}
100 93
101=head1 FUNCTIONAL INTERFACE 94=head1 FUNCTIONAL INTERFACE
102 95
103The following convinience methods are provided by this module. They are 96The following convinience methods are provided by this module. They are
104exported by default: 97exported by default:
126This function call is functionally identical to: 119This function call is functionally identical to:
127 120
128 $perl_scalar = JSON::XS->new->utf8->decode ($json_text) 121 $perl_scalar = JSON::XS->new->utf8->decode ($json_text)
129 122
130except being faster. 123except being faster.
124
125=item $is_boolean = JSON::XS::is_bool $scalar
126
127Returns true if the passed scalar represents either JSON::XS::true or
128JSON::XS::false, two constants that act like C<1> and C<0>, respectively
129and are used to represent JSON C<true> and C<false> values in Perl.
130
131See MAPPING, below, for more information on how JSON values are mapped to
132Perl.
131 133
132=back 134=back
133 135
134 136
135=head1 OBJECT-ORIENTED INTERFACE 137=head1 OBJECT-ORIENTED INTERFACE
276 278
277Example, space_before and indent disabled, space_after enabled: 279Example, space_before and indent disabled, space_after enabled:
278 280
279 {"key": "value"} 281 {"key": "value"}
280 282
283=item $json = $json->relaxed ([$enable])
284
285If C<$enable> is true (or missing), then C<decode> will accept some
286extensions to normal JSON syntax (see below). C<encode> will not be
287affected in anyway. I<Be aware that this option makes you accept invalid
288JSON texts as if they were valid!>. I suggest only to use this option to
289parse application-specific files written by humans (configuration files,
290resource files etc.)
291
292If C<$enable> is false (the default), then C<decode> will only accept
293valid JSON texts.
294
295Currently accepted extensions are:
296
297=over 4
298
299=item * list items can have an end-comma
300
301JSON I<separates> array elements and key-value pairs with commas. This
302can be annoying if you write JSON texts manually and want to be able to
303quickly append elements, so this extension accepts comma at the end of
304such items not just between them:
305
306 [
307 1,
308 2, <- this comma not normally allowed
309 ]
310 {
311 "k1": "v1",
312 "k2": "v2", <- this comma not normally allowed
313 }
314
315=back
316
281=item $json = $json->canonical ([$enable]) 317=item $json = $json->canonical ([$enable])
282 318
283If C<$enable> is true (or missing), then the C<encode> method will output JSON objects 319If C<$enable> is true (or missing), then the C<encode> method will output JSON objects
284by sorting their keys. This is adding a comparatively high overhead. 320by sorting their keys. This is adding a comparatively high overhead.
285 321
309Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>, 345Example, encode a Perl scalar as JSON value with enabled C<allow_nonref>,
310resulting in an invalid JSON text: 346resulting in an invalid JSON text:
311 347
312 JSON::XS->new->allow_nonref->encode ("Hello, World!") 348 JSON::XS->new->allow_nonref->encode ("Hello, World!")
313 => "Hello, World!" 349 => "Hello, World!"
350
351=item $json = $json->allow_blessed ([$enable])
352
353If C<$enable> is true (or missing), then the C<encode> method will not
354barf when it encounters a blessed reference. Instead, the value of the
355B<convert_blessed> option will decide wether C<null> (C<convert_blessed>
356disabled or no C<to_json> method found) or a representation of the
357object (C<convert_blessed> enabled and C<to_json> method found) is being
358encoded. Has no effect on C<decode>.
359
360If C<$enable> is false (the default), then C<encode> will throw an
361exception when it encounters a blessed object.
362
363=item $json = $json->convert_blessed ([$enable])
364
365If C<$enable> is true (or missing), then C<encode>, upon encountering a
366blessed object, will check for the availability of the C<TO_JSON> method
367on the object's class. If found, it will be called in scalar context
368and the resulting scalar will be encoded instead of the object. If no
369C<TO_JSON> method is found, the value of C<allow_blessed> will decide what
370to do.
371
372The C<TO_JSON> method may safely call die if it wants. If C<TO_JSON>
373returns other blessed objects, those will be handled in the same
374way. C<TO_JSON> must take care of not causing an endless recursion cycle
375(== crash) in this case. The name of C<TO_JSON> was chosen because other
376methods called by the Perl core (== not by the user of the object) are
377usually in upper case letters and to avoid collisions with the C<to_json>
378function.
379
380This setting does not yet influence C<decode> in any way, but in the
381future, global hooks might get installed that influence C<decode> and are
382enabled by this setting.
383
384If C<$enable> is false, then the C<allow_blessed> setting will decide what
385to do when a blessed object is found.
386
387=item $json = $json->filter_json_object ([$coderef->($hashref)])
388
389When C<$coderef> is specified, it will be called from C<decode> each
390time it decodes a JSON object. The only argument is a reference to the
391newly-created hash. If the code references returns a single scalar (which
392need not be a reference), this value (i.e. a copy of that scalar to avoid
393aliasing) is inserted into the deserialised data structure. If it returns
394an empty list (NOTE: I<not> C<undef>, which is a valid scalar), the
395original deserialised hash will be inserted. This setting can slow down
396decoding considerably.
397
398When C<$coderef> is omitted or undefined, any existing callback will
399be removed and C<decode> will not change the deserialised hash in any
400way.
401
402Example, convert all JSON objects into the integer 5:
403
404 my $js = JSON::XS->new->filter_json_object (sub { 5 });
405 # returns [5]
406 $js->decode ('[{}]')
407 # throw an exception because allow_nonref is not enabled
408 # so a lone 5 is not allowed.
409 $js->decode ('{"a":1, "b":2}');
410
411=item $json = $json->filter_json_single_key_object ($key [=> $coderef->($value)])
412
413Works remotely similar to C<filter_json_object>, but is only called for
414JSON objects having a single key named C<$key>.
415
416This C<$coderef> is called before the one specified via
417C<filter_json_object>, if any. It gets passed the single value in the JSON
418object. If it returns a single value, it will be inserted into the data
419structure. If it returns nothing (not even C<undef> but the empty list),
420the callback from C<filter_json_object> will be called next, as if no
421single-key callback were specified.
422
423If C<$coderef> is omitted or undefined, the corresponding callback will be
424disabled. There can only ever be one callback for a given key.
425
426As this callback gets called less often then the C<filter_json_object>
427one, decoding speed will not usually suffer as much. Therefore, single-key
428objects make excellent targets to serialise Perl objects into, especially
429as single-key JSON objects are as close to the type-tagged value concept
430as JSON gets (its basically an ID/VALUE tuple). Of course, JSON does not
431support this in any way, so you need to make sure your data never looks
432like a serialised Perl hash.
433
434Typical names for the single object key are C<__class_whatever__>, or
435C<$__dollars_are_rarely_used__$> or C<}ugly_brace_placement>, or even
436things like C<__class_md5sum(classname)__>, to reduce the risk of clashing
437with real hashes.
438
439Example, decode JSON objects of the form C<< { "__widget__" => <id> } >>
440into the corresponding C<< $WIDGET{<id>} >> object:
441
442 # return whatever is in $WIDGET{5}:
443 JSON::XS
444 ->new
445 ->filter_json_single_key_object (__widget__ => sub {
446 $WIDGET{ $_[0] }
447 })
448 ->decode ('{"__widget__": 5')
449
450 # this can be used with a TO_JSON method in some "widget" class
451 # for serialisation to json:
452 sub WidgetBase::TO_JSON {
453 my ($self) = @_;
454
455 unless ($self->{id}) {
456 $self->{id} = ..get..some..id..;
457 $WIDGET{$self->{id}} = $self;
458 }
459
460 { __widget__ => $self->{id} }
461 }
314 462
315=item $json = $json->shrink ([$enable]) 463=item $json = $json->shrink ([$enable])
316 464
317Perl usually over-allocates memory a bit when allocating space for 465Perl usually over-allocates memory a bit when allocating space for
318strings. This flag optionally resizes strings generated by either 466strings. This flag optionally resizes strings generated by either
351given character in a string. 499given character in a string.
352 500
353Setting the maximum depth to one disallows any nesting, so that ensures 501Setting the maximum depth to one disallows any nesting, so that ensures
354that the object is only a single hash/object or array. 502that the object is only a single hash/object or array.
355 503
356The argument to C<max_depth> will be rounded up to the next nearest power 504The argument to C<max_depth> will be rounded up to the next highest power
357of two. 505of two. If no argument is given, the highest possible setting will be
506used, which is rarely useful.
507
508See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
509
510=item $json = $json->max_size ([$maximum_string_size])
511
512Set the maximum length a JSON text may have (in bytes) where decoding is
513being attempted. The default is C<0>, meaning no limit. When C<decode>
514is called on a string longer then this number of characters it will not
515attempt to decode the string but throw an exception. This setting has no
516effect on C<encode> (yet).
517
518The argument to C<max_size> will be rounded up to the next B<highest>
519power of two (so may be more than requested). If no argument is given, the
520limit check will be deactivated (same as when C<0> is specified).
358 521
359See SECURITY CONSIDERATIONS, below, for more info on why this is useful. 522See SECURITY CONSIDERATIONS, below, for more info on why this is useful.
360 523
361=item $json_text = $json->encode ($perl_scalar) 524=item $json_text = $json->encode ($perl_scalar)
362 525
402 565
403For the more enlightened: note that in the following descriptions, 566For the more enlightened: note that in the following descriptions,
404lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl> 567lowercase I<perl> refers to the Perl interpreter, while uppcercase I<Perl>
405refers to the abstract Perl language itself. 568refers to the abstract Perl language itself.
406 569
570
407=head2 JSON -> PERL 571=head2 JSON -> PERL
408 572
409=over 4 573=over 4
410 574
411=item object 575=item object
423are represented by the same codepoints in the Perl string, so no manual 587are represented by the same codepoints in the Perl string, so no manual
424decoding is necessary. 588decoding is necessary.
425 589
426=item number 590=item number
427 591
428A JSON number becomes either an integer or numeric (floating point) 592A JSON number becomes either an integer, numeric (floating point) or
429scalar in perl, depending on its range and any fractional parts. On the 593string scalar in perl, depending on its range and any fractional parts. On
430Perl level, there is no difference between those as Perl handles all the 594the Perl level, there is no difference between those as Perl handles all
431conversion details, but an integer may take slightly less memory and might 595the conversion details, but an integer may take slightly less memory and
432represent more values exactly than (floating point) numbers. 596might represent more values exactly than (floating point) numbers.
597
598If the number consists of digits only, JSON::XS will try to represent
599it as an integer value. If that fails, it will try to represent it as
600a numeric (floating point) value if that is possible without loss of
601precision. Otherwise it will preserve the number as a string value.
602
603Numbers containing a fractional or exponential part will always be
604represented as numeric (floating point) values, possibly at a loss of
605precision.
606
607This might create round-tripping problems as numbers might become strings,
608but as Perl is typeless there is no other way to do it.
433 609
434=item true, false 610=item true, false
435 611
436These JSON atoms become C<0>, C<1>, respectively. Information is lost in 612These JSON atoms become C<JSON::XS::true> and C<JSON::XS::false>,
437this process. Future versions might represent those values differently, 613respectively. They are overloaded to act almost exactly like the numbers
438but they will be guarenteed to act like these integers would normally in 614C<1> and C<0>. You can check wether a scalar is a JSON boolean by using
439Perl. 615the C<JSON::XS::is_bool> function.
440 616
441=item null 617=item null
442 618
443A JSON null atom becomes C<undef> in Perl. 619A JSON null atom becomes C<undef> in Perl.
444 620
445=back 621=back
622
446 623
447=head2 PERL -> JSON 624=head2 PERL -> JSON
448 625
449The mapping from Perl to JSON is slightly more difficult, as Perl is a 626The mapping from Perl to JSON is slightly more difficult, as Perl is a
450truly typeless language, so we can only guess which JSON type is meant by 627truly typeless language, so we can only guess which JSON type is meant by
475C<1>, which get turned into C<false> and C<true> atoms in JSON. You can 652C<1>, which get turned into C<false> and C<true> atoms in JSON. You can
476also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability. 653also use C<JSON::XS::false> and C<JSON::XS::true> to improve readability.
477 654
478 to_json [\0,JSON::XS::true] # yields [false,true] 655 to_json [\0,JSON::XS::true] # yields [false,true]
479 656
657=item JSON::XS::true, JSON::XS::false
658
659These special values become JSON true and JSON false values,
660respectively. You cna alos use C<\1> and C<\0> directly if you want.
661
480=item blessed objects 662=item blessed objects
481 663
482Blessed objects are not allowed. JSON::XS currently tries to encode their 664Blessed objects are not allowed. JSON::XS currently tries to encode their
483underlying representation (hash- or arrayref), but this behaviour might 665underlying representation (hash- or arrayref), but this behaviour might
484change in future versions. 666change in future versions.
605 787
606Does not check input for validity. 788Does not check input for validity.
607 789
608=back 790=back
609 791
792
793=head2 JSON and YAML
794
795You often hear that JSON is a subset (or a close subset) of YAML. This is,
796however, a mass hysteria and very far from the truth. In general, there is
797no way to configure JSON::XS to output a data structure as valid YAML.
798
799If you really must use JSON::XS to generate YAML, you should use this
800algorithm (subject to change in future versions):
801
802 my $to_yaml = JSON::XS->new->utf8->space_after (1);
803 my $yaml = $to_yaml->encode ($ref) . "\n";
804
805This will usually generate JSON texts that also parse as valid
806YAML. Please note that YAML has hardcoded limits on (simple) object key
807lengths that JSON doesn't have, so you should make sure that your hash
808keys are noticably shorter than the 1024 characters YAML allows.
809
810There might be other incompatibilities that I am not aware of. In general
811you should not try to generate YAML with a JSON generator or vice versa,
812or try to parse JSON with a YAML parser or vice versa: chances are high
813that you will run into severe interoperability problems.
814
815
610=head2 SPEED 816=head2 SPEED
611 817
612It seems that JSON::XS is surprisingly fast, as shown in the following 818It seems that JSON::XS is surprisingly fast, as shown in the following
613tables. They have been generated with the help of the C<eg/bench> program 819tables. They have been generated with the help of the C<eg/bench> program
614in the JSON::XS distribution, to make it easy to compare on your own 820in the JSON::XS distribution, to make it easy to compare on your own
618single-line JSON string: 824single-line JSON string:
619 825
620 {"method": "handleMessage", "params": ["user1", "we were just talking"], \ 826 {"method": "handleMessage", "params": ["user1", "we were just talking"], \
621 "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]} 827 "id": null, "array":[1,11,234,-5,1e5,1e7, true, false]}
622 828
623It shows the number of encodes/decodes per second (JSON::XS uses the 829It shows the number of encodes/decodes per second (JSON::XS uses
624functional interface, while JSON::XS/2 uses the OO interface with 830the functional interface, while JSON::XS/2 uses the OO interface
625pretty-printing and hashkey sorting enabled). Higher is better: 831with pretty-printing and hashkey sorting enabled, JSON::XS/3 enables
832shrink). Higher is better:
626 833
834 Storable | 15779.925 | 14169.946 |
835 -----------+------------+------------+
627 module | encode | decode | 836 module | encode | decode |
628 -----------|------------|------------| 837 -----------|------------|------------|
629 JSON | 7645.468 | 4208.613 | 838 JSON | 4990.842 | 4088.813 |
630 JSON::DWIW | 68534.379 | 79437.576 | 839 JSON::DWIW | 51653.990 | 71575.154 |
631 JSON::PC | 65948.176 | 78251.940 | 840 JSON::PC | 65948.176 | 74631.744 |
632 JSON::Syck | 23379.621 | 28416.694 | 841 JSON::PP | 8931.652 | 3817.168 |
842 JSON::Syck | 24877.248 | 27776.848 |
633 JSON::XS | 388361.481 | 199728.762 | 843 JSON::XS | 388361.481 | 227951.304 |
634 JSON::XS/2 | 218453.333 | 192399.266 | 844 JSON::XS/2 | 227951.304 | 218453.333 |
635 JSON::XS/3 | 338250.323 | 192399.266 | 845 JSON::XS/3 | 338250.323 | 218453.333 |
636 Storable | 15732.573 | 28571.553 | 846 Storable | 16500.016 | 135300.129 |
637 -----------+------------+------------+ 847 -----------+------------+------------+
638 848
639That is, JSON::XS is about five times faster than JSON::DWIW on encoding, 849That is, JSON::XS is about five times faster than JSON::DWIW on encoding,
640about three times faster on decoding, and over fourty times faster 850about three times faster on decoding, and over fourty times faster
641than JSON, even with pretty-printing and key sorting. It also compares 851than JSON, even with pretty-printing and key sorting. It also compares
644Using a longer test string (roughly 18KB, generated from Yahoo! Locals 854Using a longer test string (roughly 18KB, generated from Yahoo! Locals
645search API (http://nanoref.com/yahooapis/mgPdGg): 855search API (http://nanoref.com/yahooapis/mgPdGg):
646 856
647 module | encode | decode | 857 module | encode | decode |
648 -----------|------------|------------| 858 -----------|------------|------------|
649 JSON | 254.685 | 37.665 | 859 JSON | 55.260 | 34.971 |
650 JSON::DWIW | 1014.244 | 1087.678 | 860 JSON::DWIW | 825.228 | 1082.513 |
651 JSON::PC | 3602.116 | 2307.352 | 861 JSON::PC | 3571.444 | 2394.829 |
652 JSON::Syck | 558.035 | 776.263 | 862 JSON::PP | 210.987 | 32.574 |
653 JSON::XS | 5747.196 | 3543.684 | 863 JSON::Syck | 552.551 | 787.544 |
654 JSON::XS/2 | 3968.121 | 3589.170 | 864 JSON::XS | 5780.463 | 4854.519 |
655 JSON::XS/3 | 6105.246 | 3561.134 | 865 JSON::XS/2 | 3869.998 | 4798.975 |
656 Storable | 4456.337 | 5320.020 | 866 JSON::XS/3 | 5862.880 | 4798.975 |
867 Storable | 4445.002 | 5235.027 |
657 -----------+------------+------------+ 868 -----------+------------+------------+
658 869
659Again, JSON::XS leads by far. 870Again, JSON::XS leads by far (except for Storable which non-surprisingly
871decodes faster).
660 872
661On large strings containing lots of high unicode characters, some modules 873On large strings containing lots of high unicode characters, some modules
662(such as JSON::PC) seem to decode faster than JSON::XS, but the result 874(such as JSON::PC) seem to decode faster than JSON::XS, but the result
663will be broken due to missing (or wrong) unicode handling. Others refuse 875will be broken due to missing (or wrong) unicode handling. Others refuse
664to decode or encode properly, so it was impossible to prepare a fair 876to decode or encode properly, so it was impossible to prepare a fair
677Second, you need to avoid resource-starving attacks. That means you should 889Second, you need to avoid resource-starving attacks. That means you should
678limit the size of JSON texts you accept, or make sure then when your 890limit the size of JSON texts you accept, or make sure then when your
679resources run out, thats just fine (e.g. by using a separate process that 891resources run out, thats just fine (e.g. by using a separate process that
680can crash safely). The size of a JSON text in octets or characters is 892can crash safely). The size of a JSON text in octets or characters is
681usually a good indication of the size of the resources required to decode 893usually a good indication of the size of the resources required to decode
682it into a Perl structure. 894it into a Perl structure. While JSON::XS can check the size of the JSON
895text, it might be too late when you already have it in memory, so you
896might want to check the size before you accept the string.
683 897
684Third, JSON::XS recurses using the C stack when decoding objects and 898Third, JSON::XS recurses using the C stack when decoding objects and
685arrays. The C stack is a limited resource: for instance, on my amd64 899arrays. The C stack is a limited resource: for instance, on my amd64
686machine with 8MB of stack size I can decode around 180k nested arrays but 900machine with 8MB of stack size I can decode around 180k nested arrays but
687only 14k nested JSON objects (due to perl itself recursing deeply on croak 901only 14k nested JSON objects (due to perl itself recursing deeply on croak
692 906
693And last but least, something else could bomb you that I forgot to think 907And last but least, something else could bomb you that I forgot to think
694of. In that case, you get to keep the pieces. I am always open for hints, 908of. In that case, you get to keep the pieces. I am always open for hints,
695though... 909though...
696 910
911If you are using JSON::XS to return packets to consumption
912by javascript scripts in a browser you should have a look at
913L<http://jpsykes.com/47/practical-csrf-and-json-security> to see wether
914you are vulnerable to some common attack vectors (which really are browser
915design bugs, but it is still you who will have to deal with it, as major
916browser developers care only for features, not about doing security
917right).
918
697 919
698=head1 BUGS 920=head1 BUGS
699 921
700While the goal of this module is to be correct, that unfortunately does 922While the goal of this module is to be correct, that unfortunately does
701not mean its bug-free, only that I think its design is bug-free. It is 923not mean its bug-free, only that I think its design is bug-free. It is
702still relatively early in its development. If you keep reporting bugs they 924still relatively early in its development. If you keep reporting bugs they
703will be fixed swiftly, though. 925will be fixed swiftly, though.
704 926
705=cut 927=cut
706 928
929our $true = do { bless \(my $dummy = 1), "JSON::XS::Boolean" };
930our $false = do { bless \(my $dummy = 0), "JSON::XS::Boolean" };
931
707sub true() { \1 } 932sub true() { $true }
708sub false() { \0 } 933sub false() { $false }
934
935sub is_bool($) {
936 UNIVERSAL::isa $_[0], "JSON::XS::Boolean"
937# or UNIVERSAL::isa $_[0], "JSON::Literal"
938}
939
940XSLoader::load "JSON::XS", $VERSION;
941
942package JSON::XS::Boolean;
943
944use overload
945 "0+" => sub { ${$_[0]} },
946 "++" => sub { $_[0] = ${$_[0]} + 1 },
947 "--" => sub { $_[0] = ${$_[0]} - 1 },
948 fallback => 1;
709 949
7101; 9501;
711 951
712=head1 AUTHOR 952=head1 AUTHOR
713 953

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